Chapter 3 Tissues
Body Tissues Cells are specialized for particular functions Tissues - groups of cells with similar structure and function Four primary tissue types: Epithelium Connective tissue Nervous tissue Muscle
Epithelial Tissues Found in different areas Body coverings Body linings Glandular tissue Functions Protection Absorption Filtration Secretion
Epithelium Characteristics Cells fit closely together Tissue layer always has one free surface The lower surface is bound by a basement membrane Avascular (have no blood supply) Regenerate easily if well nourished
Classification of Epithelium Number of cell layers Simple one layer Stratified more than one layer
Classification of Epithelium Shape of cells Squamous flattened Cuboidal cubeshaped Columnar column-like
Simple Epithelium Simple squamous Single layer of flat cells Usually forms membranes Lines body cavities Lines lungs and capillaries
Simple Epithelium Simple cuboidal Single layer of cube-like cells Common in glands and their ducts Forms walls of kidney tubules Covers the ovaries
Simple Epithelium Simple columnar Single layer of tall cells Often includes goblet cells, which produce mucus Lines digestive tract
Simple Epithelium Pseudostratified Single layer, but some cells are shorter than others Often looks like a double cell layer Sometimes ciliated, such as in the respiratory tract May function in absorption or secretion
Stratified Epithelium Stratified squamous Cells at the free edge are flattened Found as a protective covering where friction is common Locations Skin Mouth Esophagus
Stratified Epithelium Stratified cuboidal Two layers of cuboidal cells Stratified columnar Surface cells are columnar, cells underneath vary in size and shape Stratified cuboidal and columnar Rare in human body Found mainly in ducts of large glands
Stratified Epithelium Transitional epithelium Shape of cells depends upon the amount of stretching Lines organs of the urinary system
Glandular Epithelium Gland one or more cells that secretes a particular product Two major gland types: Endocrine gland Ductless Secretions are hormones Exocrine gland Empty through ducts to the epithelial surface Include sweat and oil glands
Connective Tissue Found everywhere in the body Includes the most abundant and widely distributed tissues Functions Binds body tissues together Supports the body Provides protection
Connective Tissue Characteristics Variations in blood supply Some tissue types are well vascularized Some have poor blood supply or are avascular Extracellular matrix Non-living material that surrounds living cells
Extracellular Matrix Two main elements: Ground substance mostly water along with adhesion proteins and polysaccharide molecules Fibers Produced by the cells Three types: Collagen fibers Elastic fibers Reticular fibers
Connective Tissue Types Bone (osseous tissue) Composed of: Bone cells in lacunae (cavities) Hard matrix of calcium salts Large numbers of collagen fibers Used to protect and support the body
Connective Tissue Types Hyaline cartilage Most common cartilage Composed of: Abundant collagen fibers Rubbery matrix Entire fetal skeleton is hyaline cartilage
Connective Tissue Types Elastic cartilage Provides elasticity Example: supports the external ear
Connective Tissue Types Fibrocartilage Highly compressible Example: forms cushion-like discs between vertebrae
Connective Tissue Types Dense connective tissue Main matrix element is collagen fibers Cells are fibroblasts Examples Tendon attach muscle to bone Ligaments attach bone to bone
Connective Tissue Types Areolar connective tissue Most widely distributed connective tissue Soft, pliable tissue Contains all fiber types Can soak up excess fluid
Connective Tissue Types Adipose tissue Matrix is an areolar tissue in which fat globules predominate Many cells contain large lipid deposits Functions Insulates the body Protects some organs Serves as a site of fuel storage
Connective Tissue Types Reticular connective tissue Delicate network of interwoven fibers Forms stroma (internal supporting network) of lymphoid organs Lymph nodes Spleen Bone marrow
Connective Tissue Types Blood Blood cells surrounded by fluid matrix Fibers are visible during clotting Functions as the transport vehicle for materials
Muscle Tissue Function is to produce movement Three types: Skeletal muscle Cardiac muscle Smooth muscle
Muscle Tissue Types Skeletal muscle Can be controlled voluntarily Cells attach to connective tissue Cells are striated Cells have more than one nucleus
Muscle Tissue Types Cardiac muscle Found only in the heart Function is to pump blood (involuntary) Cells attached to other cardiac muscle cells at intercalated disks Cells are striated One nucleus per cell
Muscle Tissue Types Smooth muscle Involuntary muscle Surrounds hollow organs Attached to other smooth muscle cells No visible striations One nucleus per cell
Nervous Tissue Neurons and nerve support cells Function is to send impulses to other areas of the body Irritability Conductivity
Tissue Repair Regeneration Replacement of destroyed tissue by the same kind of cells Fibrosis Repair by dense fibrous connective tissue (scar tissue) Determination of method Type of tissue damaged Severity of the injury
Events in Tissue Repair Capillaries become very permeable Introduce clotting proteins Wall off injured area Formation of granulation tissue Regeneration of surface epithelium
Regeneration of Tissues Tissues that regenerate easily Epithelial tissue Fibrous connective tissue and bone Tissues that regenerate poorly Skeletal muscle Tissues that are replaced largely with scar tissue Cardiac muscle Nervous tissue within the brain and spinal cord
Developmental Aspects of Tissue Epithelial tissue arises from all three primary germ layers Muscle and connective tissue arise from the mesoderm Nervous tissue arises from the ectoderm With old age there is a decrease in mass and viabililty in most tissues